We will test the efficacy of an innovative treatment technique that could induce a radical paradigm shift in movement rehabilitation for people with Parkinson disease (PD). Based upon an extremely successful speech treatment for people with idiopathic PD (the Lee Silverman Voice Treatment (LSVT(R)), people with PD will undergo intensive practice of high effort/large amplitude arm movements and learn to transfer their "big effort" to everyday movements. Unlike other physical therapy approaches with unclear efficacy, the LSVT(R) approach has clearly demonstrated both short and long term efficacy up to two years. In addition, LSVT(R) is supported by hypotheses put forth to explain hypokinesia and bradykinesia in people with PD, therefore, it is easily applied to limb movements. Fifty subjects will be randomly assigned to one of two interventions with similar intensity regimens, think big therapy (novel) or traditional physical therapy (control). Speech studies have shown that a treatment with a simple focus (think loud) may generalize to affect motor output in other systems (e.g., articulation, speaking rate, swallowing, respiratory mechanics). Thus, we predict that learning to perform bigger arm movements will also improve arm speed, based upon the well described relationship between movement speed and amplitude. In addition, we will document the generalizability of this technique to improve arm and leg function. Although both groups may show improvements given the intense work schedule, we predict that improvements in the think big therapy will be greater than in the traditional physical therapy (control) group. Measurements will include physiological tests for assessing arm movement speed and amplitude using kinematic techniques. As "sense of effort" is the primary proposed mechanism underlying this treatment approach, we will measure sense of effort. Additional measurements will include tests of arm and leg function (strength, timed ADL tasks, gait, handwriting), a standardized clinical assessment (UPDRS), and a subjective rating scale. If successful, we plan to 1) further validate retention of treatment effects and generalizability of this technique (speech to limb; limb to speech) and 2) develop a standardized protocol that can be used for training physical therapists.